Why Would Biff

Consider that he graduated high school in June 1956, so he only waited two years to really cash in on the almanac. Not sure what the gambling laws in California were at that point, it might have been 21. The video in his museum said he won his first million on his 21st birthday.

Lot of possibilities as to why Biff didn't make more sooner. Maybe he was still nervous about using it, and needed time to work up the nerve to do it. Or maybe he started out with small time bookies, just testing it out, and trying earn enough money to make that big bet. Also maybe that was the first chance to had to really win big. He saw that a long shot was going to win, and that's where he could cash in.

Not to mention, "It's leave! Make like a tree and leave! You sound like a damn fool when you say it wrong!" Heck, he only graduated because George did most of his school work. After George stood upto him after Marty interfered with things, and would not do his homework for him anymore, he probably barely passed every subject with a few Cs and probably a few Ds.

He would not make it in today's world now that some schools have gotten rid of the grade D (at least in my area of Southern Illinois) so that you have to pass with a C or above.

I love when he corrects him on "Make like a tree and LEAVE!" Always made me wonder when Old Biff was corrected on that.

1) He had to pick an exact date where he remembered exactly where he would be, and what he was doing, and the minimum number of people would see him and potential interfere.

2) It was a significant date in the space time continum.

3) Or just an amazing coincidence.